Royal Enfield 1570197/C – Cylinder Head Bolt M10 x 181mm (OEM) for Classic 350, Bullet 350, Hunter 350 J SERIES UK/Euro V

Keep your cylinder head securely fastened with the genuine Royal Enfield 1570197/C Cylinder Head Bolt (M10 × 181). This OEM bolt is designed to factory tolerances in thread size, length, strength, and material (high-grade steel) to safely hold the cylinder head to the barrel under combustion pressures. If your existing bolt is rusty, stretched, damaged threads, or you’ve had cooling gasket leakage, this replacement restores proper sealing and structural integrity.

Manufactured for Re’s newer 349cc J-Series single-cylinder engines, this M10 × 181 mm bolt is confirmed to fit Classic 350, Bullet 350, Hunter 350 (UK / Euro V trims) among others listed by Iron City Motorcycles. The bolt’s correct length (“181”) is critical—too short and you risk insufficient clamping; too long and it can bottom out or interfere. Sold as a single OEM bolt, this part ensures you get factory-specified thread pitch, coating, and strength.

Key Features:

• Genuine Royal Enfield OEM 1570197/C Cylinder Head Bolt – size M10 x 181mm. 

• Factory-grade material & coating to resist heat and corrosion. 

• Exact bolt length and thread pitch for J-Series 349cc heads. 

• Critical for proper clamping of cylinder head to barrel to prevent limp-engine, head gasket failure, or misalignment.

• OEM fitensures correct seating, torque spec compatibility, and improved engine reliability.

• Sold individually (single bolt).

Compatibility Table :

Variants:

• Part Number Variants: 1570197/B vs 1570197/C – both labelled “Bolt, Cylinder Head – M10 x 181”. The /C version may have a different coating or revision than /B. 

• Finish / Coating: Possibly different (e.g. zinc coated vs stainless / heat-treated) — /C tends to show higher price, suggesting upgraded or revised version. 

• Quantity: Single bolt.

FAQs:

1. How can I check if 1570197/C is the correct head bolt for my motorcycle?
   → Remove the existing cylinder head bolt and inspect for markings (stamped number). Measure bolt length from under the head to end: it should be ~181 mm. Also check thread pitch & M10 head size. If your current bolt is marked 1570197/B or 1570197/C, and bolt geometry matches, /C is correct.

2. What's the difference between 1570197/B and 1570197/C?
   → Both are cylinder head bolts of the same thread and size. The difference is in “revision / finish / coating / batch revision” possibly offering improved durability or coating in /C. /C is generally a more recent or upgraded version.

3. Is this bolt critical for maintaining engine performance and sealing?
   → Yes. The cylinder head bolt clamps the head to the barrel; incorrect bolt (wrong length or strength) can cause head gasket leaks, warping, or loosening under heat cycles. OEM spec is essential.

4. Will using a non-OEM or cheaper bolt cause issues?
   → Potentially yes. Cheaper bolts may use lower tensile spec, incorrect heat treatment, low-quality coating. They can stretch, fail, or corrode, leading to leaks or engine damage.

5. Do I need any torque spec or re-torque after installation?
   → Yes. Use manufacturer prescribed torque settings. After first heat cycle, check bolt torque. In many RE J-Series engines, cylinder head bolts are torque-to-yield or stretch type – check manual. Using OEM bolt, proper torque, and sequence is essential.